Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 31, 1999
Publication Date: N/A
Polyamines have been implicated in many aspects of plant growth and development. They are involved in anabolic and growth processes and seem to prevent plant senescence. The ripening hormone ethylene and polyamine biosyntheses use a common intermediate, S-adenosylmethionine (SAM). SAM decarboxylase (SAMdc), a key enzyme in promoting accumulation of polyamines during plant growth, decreases in activity during ripening. To test whether tomato fruit metabolism could be modulated by an increase in the polyamine levels, we transformed tomato plants with the coding sequence of the yeast SAMdc fused to the promoter of the ripening and ethylene-responsive gene, E-8. Compared to the azygous lines, ripe fruits from three transgenic lines accumulate four- to six-fold more spermidine. Fruits from two of these transgenic lines show delayed ripening and accumulate several-fold higher lycopene content than the control fruits. Surprisingly, despite the accumulation of spermidine, the homozygous transgenic tomato fruits consistently produced more ethylene than the azygous lines. We are currently testing various possibilities that could explain these results.